The space-based component of the Global Observing System that is mainly composed of low earth orbiting (LEO) and geostationary (GEO) satellites. LEO satellites circle the earth in fixed sun synchronous orbits with their instruments scanning in a prescribed manner; they provide global observations daily with the same solar illumination geometry. GEO satellites are stationary over prescribed longitudes on the equator with their instruments scanning in various programmable modes; they provide hemispheric observations routinely at hourly or less intervals with changing solar illumination. Microwave observations to date are exclusive to LEO systems. Optimal synergy between the GEO and LEO systems emphasizes the advantages of each orbit and the associated spectral, spatial, and temporal coverage. Intercalibration of the systems strengthens the utility of both. Thoughts and strategy regarding the complementarity of the two systems will be presented.